The invention relates to a drive device or transmission, which may for example be employed in the pneumatic equipment sector as a valve drive.
In connection with valves serving for the control of fluid flows in the pneumatic equipment sector so far as a rule valve drives have been utilized, which are constituted by electromagnets or piezoelectric transducers. While being suitable for the transmission of large forces such drives generally only perform a drive movement with relatively small force strokes. Furthermore, there are design limitations as regards presetting the force-stroke characteristic, this restricting the field of application.
One object of the invention is to create a drive device whose characteristics are able to be varied using comparatively simple means and which in case of need renders possible performing drive movements with a large force and simultaneously a large stroke.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, the present invention provides at least one drive unit, which comprises two mutually spaced pressing bodies on which facing pressing faces are provided, which diverge in a drive direction and between which a stroke unit is located engaging the pressing faces of the two pressing bodies, and furthermore drive means for causing a mutual motion together of the pressing bodies and a displacement, resulting therefrom of the stroke unit in the drive direction along the pressing faces for the production of a drive movement which can be utilized externally.
The drive device thus comprises at least one drive unit, which possesses a stroke unit, which is arranged between the pressing faces, which are moving apart, of two spaced pressing bodies. By way of drive means cooperating with one or both pressing bodies it is possible for the pressing bodies to be so moved in relation to one another that the pressing faces draw closer together. Owing to their diverging configuration this results in a displacement of the stroke unit in a direction athwart the direction of movement together of the pressing faces, the direction of displacement being termed the drive direction. The stroke unit is practically displaced out of the way by the pressing faces acting on it, there being a redirecting of the force in the said drive direction. The displacement of the stroke unit may then be utilized externally as a drive movement, which acts directly or indirectly on a component to be moved, as for example on the valve member to be actuated of a control valve.
Because the configuration of the pressing faces can be preset in a predetermined manner by the manufacturer, drive devices with a customized adaptation of the force-stroke characteristic may be produced in a relatively simple fashion. Inherently means may be employed as a drive which produces only a small stroke but a high actuating force, the design of the pressing faces being able to be configured to yield a transmission ratio, which converts a relatively small stroke of the drive means into a sufficiently large stroke of the drive movement able to be employed as an output. It is for this reason that the drive device is particularly suitable for the production of small and miniature designs, a piezoelectric transducer device means being for example employed as a drive means. As an alternative it would be possible as well to use drive means operated by fluid power as are supplied by the assignee under the trade name of xe2x80x9cFluidic Musclesxe2x80x9d.
The drive device offers the further advantage that it may in case of need be so designed and operated that it provides for a constant drive characteristic and different stroke positions of the stroke unit may be set in a stepless manner.
Further advantageous developments of the invention are defined in the claims.
The two pressing bodies are preferably moved toward each other by activation of the drive means starting from a home position, the pressing face of at least one, and preferably both of the pressing bodies being so shaped that as considered in the home position, there is an inclination of the faces in relation to the drive direction produced.
In the simplest case the pressing faces present are in the form of oblique faces with a linear form. By presetting the angle of inclination in relation to the drive direction it is possible for the transmission ratio or, respectively, the force-stroke characteristic to be predetermined. In order to produce customized drive movements, the pressing faces may be also provided with a curved shape in order to produce a non-linear motion characteristic.
The drive device may in principle be so designed that the relative movement of the two pressing bodies is produced by the movement of only one pressing body, the other pressing body remaining stationary and for instance being fixedly attached to an associated housing part. However it is preferred to have a design which ensures simultaneous motion of the two pressing bodies during movement together.
The mutual movement together of the pressing faces is preferably produced by a pivoting movement of one or both pressing bodies. For this purpose the pressing bodies may be coupled together in a pivoting manner in relation to one another in a bearing zone and extend approximately in the same direction away from the bearing zone, and furthermore delimit a pressing space wherein the moving stroke unit is located. The drive means are in this case preferably placed at the bearing zone, a pull and/or thrust action being provided in a manner dependent on the side of the application of the drive forces in order to cause a pivoting action of at least one pressing body.
It is particularly advantageous for a piezoelectric transducer means to be installed, which possesses at least two stack translators connected in parallel and rendering possible a simultaneous opposite operation so that on the one side of the pivot zone a pulling force is produced and on the other side at the same time a thrust force may be exerted on the pressing bodies. It would for instance be possible to utilize a piezoelectric transducer means as sold by the company xe2x80x9cmarco Systemanalyse und Entwicklung GmbHxe2x80x9d, of 85221 Dachau, Germany under the name of xe2x80x9cTorque-Blocksxe2x80x9d.
In order to produce the return motion, opposite to the drive movement, of the stroke unit it is possible to use a passive spring means instead of an active actuating means. This spring means could act between the pressing bodies and/or engage the stroke unit.
Principally it would be feasible as well to design the stroke unit like a slide so that it could be displaced on the pressing faces as part of a sliding movement. In order to ensure a reliable manner of operation with minimum friction it is however preferred to utilize a stroke unit in the form of a rolling body unit, which during its drive movement rolls on the pressing faces of the pressing bodies. In order to prevent jamming in this connection the rolling body unit comprises more particularly at least two independently rotatable rolling bodies, which respectively engage only one of the pressing faces on the two pressing bodies so that the one rolling body may roll on the pressing face of the one pressing body and the other rolling body may roll on the pressing face of the other pressing body.
In the case of a further and more particularly advantageous embodiment of the invention the drive device is provided with two drive units, which are fitted together as an assembly, the pressing bodies of the two drive units being so fitted together in pairs as two flexurally rigid pressing elements that the pressing faces of the two drive units run apart from opposite sides which face away from the one another. Using a connecting yoke it is possible then for the two stroke units present to be so kinematically coupled that during a drive movement of the respectively one stroke unit the respectively other stroke unit is entrained and practically performs the return movement.
The two pressing elements are mounted in a bearing zone preferably in a relatively pivoting manner so that a rocking or see-saw movement of one or both pressing elements may be caused, always resulting in a movement together of the pressing faces and simultaneously a movement apart of the pressing faces of the other drive unit. In the case of a particularly economic design the drive units are arranged with bilateral symmetry with respect to the bearing zone.
The drive movement produced can be transmitted to other means from any point of the movement unit constituted by the stroke unit and the connecting yoke. It is more especially convenient however for such output drive movement to be taken from the connecting yoke and preferably in the area at the mid point the between the two stroke units.
In order to prevent jamming on shifting the movement unit it has turned out to be expedient to make the connecting yoke so resiliently elastic in its stroke direction that small relative movements of the two stroke units are possible in the direction of the motion produced. This means that inaccuracies in manufacture are compensated for.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof with possible modifications in conjunction with the accompanying drawings.